1. Field of the Invention
The present invention relates to adsorbents used for cleaning (deodorizing, decoloring and extracting impurities) of gases and liquids or for various other applications, methods for producing the same and applications thereof.
More specifically, the present invention relates to indoor ambient air cleaning members, methods for cleaning air, air cleaning devices, dehumidifying materials for inner gas of dual-glass window, drying agents for organic solvents, adsorbents for hard disk drives and freshness keeping member, all of which utilize the adsorbents.
The present invention also relates to ambiance humidity regulating members that provide controlled humidity of the ambiance when it is placed therein.
2. Related Prior Art
Adsorbents that are supported on a porous base member such as net sheets, fibers, foams and so on by utilizing binders and the like are known in the art. The adsorbents are utilized to carry out cleaning processing of gases and liquids. Since conventional adsorbent materials are porous materials themselves and have brittle surfaces, dust particles are generated upon exerting mechanical loads thereon, thereby contaminating the target gases and liquids with the dust particles.
The Japanese Patent Unexamined Publication No. H11-57,377 discloses that the contamination with the dust particles can be prevented by introducing an absorbing material within a vessel that sealingly contains a perforated sheet having permeability to air. However, breakage or pinhole tends to be occurred in the perforated sheet to easily release the generated dust particles.
Increasing capacity of and miniaturization of hard disk (hereinafter called as “HD”), one of storage devices, are rapidly advanced in recent years, and the levels of the requirements for the hard disk drive (hereinafter called as “HDD”), finished products of the HD, are increasing from year to year. The required performances for the HDD include better dehumidifying and maintaining cleanliness within the HDD. These performances are required because a contamination within the HDD generally leads to disk errors, damages of HD and damages of magnetic heads thereof. Therefore, it would be ideal to eliminate the contamination source such as organic gases from the interior of the HDD. However in reality, since the HDD includes a number of parts therein that contain adhesives for assembling thereof, contamination particles and gases are generated from the parts assembled therein or adhesives, thereby generally contaminating the interior of the HDD.
In order to prevent such contamination, technologies of adsorbing and removing the generated gases are disclosed. For example, the Japanese Application Unexamined Publications No. H10-321 and No. H11-57,377 disclose adsorbents in which an adsorbing material is closely packed within a container formed of porous PTFE (polytetrafluoroethylene) films. The adsorbents described in these Publications comprise an adsorbing material closely packed by PTFE films, for the purpose of removing the gases generated from the interior of the HDD by the adsorbing material and preventing the interior contamination from the generated particles with the adsorbing material.
More specifically, adsorbing materials having better adsorbability generally include microscopic pores on the surfaces, and therefore the surface portions of the adsorbing material may be easily broken when a certain amount of mechanical load is exerted onto the surface by collision or sliding occurred between the adsorbing materials, thereby generating the contaminating dust. Therefore, the adsorbing material should be closely packed within a package.
However, the resin materials used for the package thereof such as PTFE film and so on are highly electrically insulative and thus, in general, electrostatically charged. Therefore, when the container is formed by the insulative material such as PTFE film and the container pocket is filled with the adsorbing material such as activated carbon or silica gel, the adsorbing material may be scattered from the container or adhered on the inside surface of the container due to the electrostatics. In this reason, it is difficult to fully fill the container with the adsorbing material without leaving dead space therein. Accordingly, the bulk volume of the adsorbing material contained in the container becomes lower and thus the problem of lower volumetric efficiency occurs in the HDD in which miniaturization thereof is required.
In addition, there may be a risk of providing insufficient sealing since the contaminating particles may be adhered onto the sealing interface of the PTFE film when the adsorbing material is packed with the PTFE film, and thus there may be a risk of contaminating the interior of the HDD.
Further, the base material of porous PTFE film for container is required to have a certain level of mechanical strength for forming the porous PTFE film to a container, and thus a corresponding thickness should be required. On the other hand, increasing the thickness of the porous film may be a factor for adversely affecting the permeability to air. In this case, there is no choice other than that the mechanical strength should be given priority over the air permeability. Thus, the adsorbability of the adsorbent contained in the container having less air permeability is, in turn, decreased.
Similar problems related to the adsorbing material and the container occur in other applications. Plants such as fruits, vegetables, flowers and so on (hereinafter called as “vegetables”) emit a trace amount of ethylene gas. The presence of ethylene gas in the storage atmosphere accelerates aging of vegetables, thereby deteriorating the freshness of the vegetables.
Japanese Application Unexamined Publication No. H02-138,935 discloses the materials for keeping freshness of the vegetables that adsorb and/or dissociate ethylene gas by activated carbon, zeolite, palladium supported carbon black or so on to keep freshness of the vegetables.
Since carbon black is a very fine powder, the carbon black may be easily scattered to easily blacken the vegetables.
Activated carbon and zeolite also easily create fine contaminating particles when they are in friction, and smudge the vegetables.
Further, since the vegetables also emit water vapor as well as ethylene gas, water condensation dew is easily generated on an interior surface of a bag container for storing vegetables. The condensed water, in turn, wets the adsorbing material such as activated carbon and zeolite, thereby significantly deteriorating the adsorbability for ethylene gas having hydrophobic nature.